September 2017
Monthly Overview - September 2017
Dry Condition for Most of Midwest
A large swath of the Midwest, extending from Missouri to Lower Michigan, received less than an inch of rain in September
(Figure 1). Totals topping four inches for the month were limited to Kentucky and extreme southern Indiana in the southeast and Minnesota and the northern tip of Wisconsin. These totals put the vast majority of the region below normal with deficits of two to four inches over large areas (Figure 2). Heavier rains in parts of Kentucky and Minnesota pushed totals to more than twice the normal amount but areas between saw less than 25% of normal in September
(Figure 3). Heavy rain fell in Kentucky as the remnants of Hurricane Harvey passed over the state on the first two days of the month(Figure 4) Statewide precipitation totals ranged from slightly above normal in Kentucky and Minnesota to less than 25% of normal in Illinois and Missouri.
Very Warm after a Cool Start
On the heels of a cool August, September started with below-normal temperatures across the Midwest
(Figure 5). After a transition period with warmth in the northwest and coolness hanging on in the southeast, temperatures were well above average for a two-week period before returning to normal in the last couple days of the month. More than 2,800 daily temperature records were set with nearly 500 record lows (Figure 6) in the first half of the month, and more than 2,000 record highs
(Figure 7) in the latter half of the month. Chicago set new record high maximum temperatures for five straight days from the 20th to the 24th. Across the Midwest, September temperatures averaged out to 1°F below normal in parts of Kentucky to more than 4°F above normal in extreme southeast Minnesota and part of neighboring Wisconsin (Figure 8). Statewide temperatures for the month were above normal in all nine states, ranging from just above normal in Kentucky (0.1°F) to more than 3°F above normal in Iowa, Minnesota, Wisconsin, and Michigan.
Drought Expands
Dry conditions for much of the region led to the slight expansion of area experiencing drought (Figure 9). The increase from just under 7.5% of the region on August 29th to just under 12% of the region on October 3rd was much smaller than the increase in area noted as abnormally dry (19% to 48%) indicating many areas on the brink of drought. Much of the increase in abnormally dry area occurred in the first half of the month. The area of extreme drought (in southern Iowa) shrunk slightly.
Severe Weather
Severe convective weather was reported on 13 days in September. All nine states were touched by severe weather but more than half of the reports were from Minnesota
(Figure 10). The other eight states had less than a couple dozen reports each, with some having just a handful of reports. Tornadoes were reported in September, on the 4th in Ohio and on the 19th in Minnesota. Two injuries were reported with the EF-2 tornado in Ohio. Hail reports were most numerous in Minnesota on the 14th, and wind reports were most numerous in Minnesota on the 19th.
Harvest Begins
The fall harvest got underway in the Midwest. As it has been for much of the 2017 growing season, conditions were hard to generalize across the region with different impacts in different parts of the region. This continued into the harvest season. Corn harvest (Figure 11) is running behind in Illinois and Iowa in particular. But soybean harvest (Figure 12) in Minnesota is well behind average while running ahead in Illinois and Michigan. Soybean harvest in Indiana and Ohio is being hampered, despite good field access, by dryness which has led to combine fires and concerns about splitting or shattering of the beans. Many in Indiana and Ohio put off their bean harvest waiting for some rain to reduce these risks.
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The Iowa Climatology Bureau also contributed to this report.
The Minnesota State Climatology Office also contributed to this report.
The Missouri Climate Center also contributed to this report.